Diester fluids containing basic sulfonates, nu-butyryl-p-amino phenol and phenothiazine



United States Patent 2,992,183 c DIES'IER FLUIDS CONTAINING BASIC SULFU- NATES, N-BUTYRYL-p-AMINO PHENOL AND PHENOTHIAZINE Robert W. Schrum, Lansing, IlL, assignor to Sinclair Refining Company, New York, N.Y., a corporation of Maine No Drawing. Filed Apr. 9, 1958, Ser. No. 727,234 3 Claims. (Cl. 252-33).4)

This invention relates to novel synthetic lubricating oil compositions. More specifically, my invention is concerned with synthetic lubricating oil compositions comprising an ester base oil of lubricating viscosity having incorporated therein an alkaline earth metal sulfonate to inhibit corrosion and a minor amount of N-butyryl-pamino phenol as an anti-oxidant. When desired, my compositions can also contain various other additives, particularly phenothiazine.

The synthetic lubricating fluids generally employed in gas turbine aircraft engines are the ester synthetic fluids of lubricating viscosity such as di-Z-ethylhexyl sebacate, sold commercially as Plexol 201-]. These synthetic oils are often designed to meet certain specifications such as the humidity cabinet corrosion test identified in MIL-C- 8l88B. To insure passage of the specification humidity cabinet test, relatively large amounts of barium sulfonate are commonly incorporated in these synthetic lubricating fluids to inhibit rust formation. Such barium sulfonatecontaining compositions, however, have been found to be difiicult to inhibit against oxidation, for instance by the use of phenothiazine, a common anti'oxidant for the ester lubricants.

It has now been discovered that incorporating a minor amount of N-butyryl-p-amino phenol with or without phenothiazine in an ester base synthetic lubricant composition containing an alkaline earth metal sulfonate as a corrosion inhibiting agent, eifectively inhibits the composition against oxidation. Accordingly, the lubricating compositions of this invention contain an amount of alkaline earth metal, e.g. barium or calcium sulfonate which imparts suflicient rust inhibition to pass the humidity cabinet test. This amount is usually in the range of about 0.1 to percent of the total composition. There does not appear to be any need for using more than 5 percent. The amount of N-butyryl-p-amino phenol added to the ester base oil sufiicient to substantially inhibit oxidation of this composition is found to be in the range of about 0.1 to 1 weight percent. When desired, other additives such as a phenothiazine anti-oxidant can also be included in the lubricant composition and ordinarily from about 0.1 to 1 weight percent of phenothiazine may be employed. The ester base oil of lubricating viscosity is the predominant component of the composition and it comprises substantially the balance considering the various additives included. On a preferred basis, the lubricants of the present invention will contain about 2 to 4 weight percent of sulfonate, about .25 to 0.5 weight percent of N-butwyl-p-amino phenol and when including phenothiazine about .25 to .5 weight percent of this ingredient. My various compositions can also contain additional agents such as other anti-oxidants, anti-foam- "ice base oils and obtained for instance, by neutralizing aromatic sulfonic acids with the hydroxides, chlorides, ox-

ides or other inorganic compounds of the alkaline earth metals. The preferred aromatic sulfom'c acids are the oil-soluble mahogany sulfonic acids which can be derived from the treatment of a suitable petroleum oil, such as a liquid petroleum distillate boiling in the range of about 600 to 1000 F., with fuming sulfuric acid or sulfur trioxide, separating the resulting acid sludge from the acid treated oil and recovering the mahogany acids contained in the acid treated oil. The useful mahogany acids generally have a molecular weight of from about 300 to 500 or more, and although their exact chemical structures may vary, it appears that such acids are composed to a large extent of sulfonated aromatic hydrocarbons having either one or two aromatic rings per molecule, possibly with one or more long-chain alkyl groups containing from about 8 to 30 carbon atomsattached to the ring nuclei.

Other suitable aromatic sulfonic acids are the oil-soluble aryl sulfonic acids; such as benzene sulfonic acids and naphthalene sulfonic acids, which include the oilsoluble alkylated aryl sulfonic acids in which the alkyl chain contains from 8 to 18 carbon atoms for instance, dinonyl naphthalene sulfonic acid, and those prepared by reaction of parafiin wax alkyl chains of 20 or more carbons with aromatic nuclei which are then sulfonated by fuming sulfuric acid, e.g. wax substituted naphthalene. The aromatic oil-soluble sulfonic acids are conveniently employed as a concentrate in the hydrocarbon from which they are derived and are usually present in approximately 10 to 30 weight percent concentration.

The alkaline earth metal sulfonates of the present invention can be neutral or basic sulfonates either of which upon addition to the syntheticv lubricant composition of my invention eifectively inhibits corrosion. By basic sulfonates is meant those sulfonates in which the alkaline earth metal is present in an amount in excess of that theoretically required to react with the sulfonic acid from. which it was made. For instance, when a basic barium sulfonate is employed as the corrosion inhibitor, there are usually at least about 1.5 equivalents of barium in the sulfonate and in the case of basic calcium sulfonate at least about 1.2 equivalents of calcium. Usually the in the sulfonate and in the case of basic calcium sulfonate basic alkaline earth metal sulfonates do not have to have more than 5 equivalents of alkaline earth metal. Also suitable as the corrosion inhibitor of my novel composition are the oil-soluble carbonated neutral or basic alkaline earth metal sulfonates.

The lubricant base oils of my compositions are the ester synthetic oils of lubricating viscosity which consist essentially of carbon, hydrogen and oxygen and include diesters and higher viscosity polyesters. Various of these lubricating materials have been described in the literature and generally their viscosity ranges from the light to heavy oils, e.g. about 30 SUS at 210 F. to 250 SUS at 210 F., and preferably 30 to 150 SUS at 210 F. The diester base oils are preferred and are made from alcohols and polycarboxylic acids, and can be thickened with complex polyesters or other polyesters of higher viscosity. Among the acids employed are those of 2 to 12 carbon atoms particularly the dicarboxylic acids such as adipic, azelaic, suberic, alkenyl succinic, sebacic, etc. The alcohols employed usually contain about 4 to 20 carbon atoms, preferably 6 to 12 carbon atoms, and are generally aliphatic such as butyl, hexyl, Z-ethylhexyl and dodecyl alcohols. The alcohols can also be polyfunctional materials such as glycols and included among the glycols are the ether glycols. Among my useful polyester base oils are those disclosed in U.S. Patents Nos. 2,499,983; 2,499,984; 2,575,195; 2,575,196; 2,703,- 311; 2,705,724; and 2,723,286.

As I have mentioned my ester base oils consist essentially of carbon, hydrogen and oxygen, that is, the essential molecular chemical structure is formed by these elements. However, these oils may be substituted with other elements such as the halogens, chlorine and fluorine, for instance, I can use the fluorinated esters of dibasic acids. Among the specific synthetic diester oils falling within the above classes are di(2-ethylhexyl) sebacate, di(2-ethylhexyl) phthalate, di(1.3-methylbutyl) adipate, di(2-ethylbutyl) adipate, di(1,3-methylbutyl) adipate, di(1-ethylpropyl) adipate, bis(14,14,7H- dodecafiuoroheptyl)-3-methyl glutarate,. di(cyclohexyl). adipate, di(undecyl) sebacate, dibenzyl. sebacate and di(2-ethylhexyl) azelate.

L The following specific examples will serve to illustrate the present invention; they are not to be considered limiting. Several synthetic lubricant compositions were prepared using Plexol 201-J as the base lubricant, into which was incorporated 2.5 or percent of either a new tral barium sulfonate or a carbonated oil-free basic barium mahogany sulfonate, 0 to 1.0 weight percent of phenothiazine and 0 to 1.0 weight percent of N-butyrylp-amino phenol. The barium sulfonates were added as a 50 percent concentrate in Plexol 201-J. Plexol 201-I is a di-Z-ethylhexyl sebacate containing 0.015 percent free sebacic acid and has a kinematic viscosity at 100 F. of about 12.7 centistokes, a viscosity index of 154, a pour point of below 80 F., and an acid number of 0.12.

The neutral barium sulfonate employed is a 50 percent concentrate of neutral barium dinonyl naphthalene sulfonate dispersed in Plexol 2014 which concentrate has the following properties:

Kinematic viscosity at 100 F 649.5 Kinematic viscosity at 210 F 14.53 Percent barium 6.45

Percent sulfur 3.33 Ba/S atoms ratio 6.49:1 Base No. to pH=4 0.56 Initial pH 7.6

The carbonated oil-free basic barium sulfonate employed was prepared as follows:

777 pounds of sulfonic acid oil, produced by a 150 lbs. oleum/bbl. treatment of dewaxed Mid-Continent 250 SUS/100 F. lube distillate was charged to an agitator and neutralized with 14.1 lbs. of aqueous ammonia. The ammonium sulfonate was extracted by mixing with 56.4 lbs. of water and 67.3 lbs. of 99 percent isopropyl alcohol at 140 F. 6000 grams of the alcohol-ammonium sulfonate extract was diluted to 8 gallons with percent isopropyl alcohol. The alcohol solution was extracted six times with 4000 cc. charges of hexane, discarding the hexane wastes. The isopropyl alcohol was then topped off to 208 F. at atmospheric pressure, leaving an oilfree sulfonate-water residue, This residue was mixed with two gallons of toluene and neutralized with 1080 grams of barium oxide (300 percent theoretical), topping off the water. The toluene solution was filtered clear. Distillation of the toluene remaining resulted in the recovery of about five pounds of mineral oil-free solid basic barium sulfonate with the following analysrs:

Percent barium 22.2

Base No. to pH=4 78.1

1513 grams of oil-free barium sulfonate was dissolved in 2323 grams of toluene and carbonated with CO gas at 100 F. and atmospheric pressure until the pH was 8.4. A 50 percent concentrate of the carbonated sulfonate in a synthetic diester which was prepared by adding 1513 grams of Plexol 201-] to the toluene solution of the sulfonate and distilling oif the toluene. The concentrate exhibited the following properties:

Kinematic viscosity at 100 F 317.9 Kinematic viscosity at 210 F 30.17 Percent barium 11.05

Percent sulfur 2.80

v Ba/S atoms ratio 0.93:1 Base No. to pH=4 37.5 Initial pH 8.4

Each of the lubricant composition samples was subjected to a humidity cabinet corrosion test. In this test, small polished mild steel panels are dipped into the synthetic lubricant composition and after draining for four hours at room temperature are suspended in a highly humid atmosphere, generally about percent humidity, at F. in a special cabinet. The time of initial corrosion of the panels is noted. The humidity cabinet is provided with heating units and thermal regulators for automatic temperature control. A water level of 8 inches is maintained in the bottom of the cabinet and 8 linear feet per hour of clean air is bubbled through the water to assure high humidity at all times. The steel panels are suspended by stainless steel hooks around the periphery of the humidity cabinet. About three complete changes of air per hour are provided in the cabinet.

The oxidation-corrosion stability of these lubricant compositions was also tested. In this test sample strips of steel, silver, aluminum alloy, magnesium alloy, and copper are separately weighed, immersed in the lubricant composition whose oxidation corrosion stability is to be tested and each subjected to a temperature of 347 F. for 72 hours while in contact with flowing air. At the end of this period the samples are weighed to determine the weight-loss or gain and examined for evidences of pitting, etching or flaking. The oil used is also tested for acid number and viscosity rise. Thme results in turn are compared to those considered acceptable according to certain pre-established specifications such as in MIL- l 8B n Ta e I.-

Table I Sample number Composition, weight percent:

P exol 201-11 Phenothiazine N-butyryl-p-amino phenoL. Barium sulfonate DOF 20060,000 5 Laboratory tests:

F., cs. V.I Acid number. Humidity cabinet test (144 hrs oxidsatiqn-corrosion stability test 7 Percent vis rise at 100 F Acid number rise .24. Etched 0.25.

MIL-C-8188B Specification Sample number Composition, weight percent:

Plexol 201-1 Phenothlazine N-butyryl-p-amino phenol Barium sulfonate 1 DCF 200-60000 3 Laboratory tests:

KV at -65 F., cs

KV at 100 F., cs.

IIIIIIIIIIIIIIIIIIIIIIIIIII Acid number Humidity cabinet test (144 hrs.) Oxidation-corrosion stability test (347 F., 72 hrs.):

Percent vis rise at 100 F Acid number rise $0.2 mgJcm. $0.2 mg./cm. =i:0.2 mg./cm. $0.2 mg./cm. i0 1 mg./cm.

MIL-C-8188B Specification Sample number Aluminum alloy Magnesium alloy 0.53 Etched 9.75 fiaked Copper Percent VS rise at 100 F Acid number rise GOO ccca rowo MQDD IQUO Sample number Composition, weight percent:

Plexol 201-3 Phenothiazine N -butyryl-p-amino phenol Barium sulfonate l Barium sulfonate 2 DCF ZOO-60,000 3 -1 Laboratory tests:

cid number KV at 100 F., cs 0xidSatio1n-corrosion stability test (347 F., 72 hrs):

tee

Acid number rise :l=0.2 rngJcm.

l.9. Etched 172.9. 6.15.

15.8, flaked.

I No pitting or etching.

Examination of the data of Table I demonstrates the 7 value of minor amounts of N-butyryl-p-amino phenol in the synthetic lubricating oil compositions of this invention. The addition of a 0.5 weight percent of N-butyrylp-amino phenol to a diester base oil of lubricating viscosity having incorporated therein about 2.5 Weight percent of barium sulfonate is seen to produce a composi-..

tion that successfully meets all the specifications of the In contrast, the addifor example, neither the addition of 0.5 or 1.0 weight percent of N-butyryl-p-amino phenol alone or phenothiazine alone gave completely satisfactory results. As the data indicate, it is preferred, when employing barium sulfonate at a 5.0 weight percent level to utilize a combination of N-butyryl-p-amino phenol and phenothiazine since the resulting compositions fully meet all specifications.

The data also show that when the sulfonate content is about 5.0 weight percent, the addition of about 1.0 weight percent of a combination of N-butyryl-p-amino phenol and phenothiazine, although meeting substantially all of the specifications may fail to meet one of them. If such is the case and it is necessary to meet all of the specifications, other anti-oxidants or additives may be needed to satisfy the requirements. In this regard, it should be pointed out that the specific amount of N-butyryl-p-amino phenol and its combination with phenothiazine to be' added to a blend may be dependent on the particular barium sulfonate employed. Each of the various barium sulfona-tes that may be employed in the present invention have their peculiar characteristics as to kinematic viscosity, basicity, percent of sulfur, etc. that may afiect the specific amounts of anti-oxidant required at a particular content of sulfonate to satisfy the oxidation-corrosion stability test.

I claim:

1. A corrosion preventative synthetic lubricant composition consisting essentially of di-Z-ethylhexyl sebacate having incorporated therein about .1 to 5.0 weight percent of carbonated oil-free basic barium mahogany sulfonate, about 0.1 to 1 Weight percent of N-butyryl-pamino phenol, and about 0.1 to 1 weight percent of phenothiazine.

2. A corrosion preventative synthetic lubricant composition consisting essentially of di-Z-ethylhexyl sebacate having incorporated therein about 2 to 4 Weight percent of carbonated oil-free basic barium mahogany sulfonate, about 0.1 to 1 Weight percent of N-butyryl-p-amino phenol, and about 0.1 to 1 weight percent of phenothiazine.

3. A corrosion preventative synthetic lubricant 'composition consisting essentially of di-Z-ethylhexyl sebacate;

having incorporated therein about 2 to 4 weight percent of carbonated oil-free basic barium mahogany sulfonate, about .25 to 0.5 weight percent of N-butyryl-p-amino phenol, and about .25 to 0.5 weight percent of pheno.-

thiazine.

References Cited in the file of this patent UNITED STATES PATENTS Wasson et a1 Mar. 11, 1947 Young et al Feb. 25, 1958 OTHER REFERENCES 

1. A CORROSION PREVENTATIVE SYNTHETIC LUBRICANT COMPOSITION CONSISTING ESSENTIALLY DI-2-ETHYLHEXYL SEBACATE HAVING INCORPORATED THEREIN ABOUT .1 TO 5.0 WEIGHT PERCENT OF CARBONATED OIL-FREE BASIC BARIUM MAHOGANY SULFONATE, ABOUT 0.1 TO 1 WEIGHT PERCENT OF N-BUTYRYL-PAMINO PHENOL, AND ABOUT 0.1 TO 1 WEIGHT PERCENT OF PHENOTHIAZINE. 